/**
 * Copyright © 2018 organization baomidou
 * <pre>
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 * <pre/>
 */
package com.baomidou.dynamic.datasource.toolkit;

/**
 * Copy from Druid https://github.com/alibaba/druid/blob/master/src/main/java/com/alibaba/druid/util/Base64.java
 */
public class Base64 {

  /**
   * This array is a lookup table that translates 6-bit positive integer index values into their
   * "Base64 Alphabet" equivalents as specified in Table 1 of RFC 2045.
   */
  private static final char intToBase64[] = {'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J', 'K',
      'L', 'M',
      'N', 'O', 'P', 'Q', 'R', 'S', 'T', 'U', 'V', 'W', 'X', 'Y', 'Z', 'a', 'b', 'c', 'd', 'e', 'f',
      'g', 'h',
      'i', 'j', 'k', 'l', 'm', 'n', 'o', 'p', 'q', 'r', 's', 't', 'u', 'v', 'w', 'x', 'y', 'z', '0',
      '1', '2',
      '3', '4', '5', '6', '7', '8', '9', '+', '/'};
  /**
   * This array is a lookup table that translates 6-bit positive integer index values into their
   * "Alternate Base64 Alphabet" equivalents. This is NOT the real Base64 Alphabet as per in Table 1
   * of RFC 2045. This alternate alphabet does not use the capital letters. It is designed for use
   * in environments where "case folding" occurs.
   */
  private static final char intToAltBase64[] = {'!', '"', '#', '$', '%', '&', '\'', '(', ')', ',',
      '-', '.', ':',
      ';', '<', '>', '@', '[', ']', '^', '`', '_', '{', '|', '}', '~', 'a', 'b', 'c', 'd', 'e', 'f',
      'g', 'h',
      'i', 'j', 'k', 'l', 'm', 'n', 'o', 'p', 'q', 'r', 's', 't', 'u', 'v', 'w', 'x', 'y', 'z', '0',
      '1', '2',
      '3', '4', '5', '6', '7', '8', '9', '+', '?'};
  /**
   * This array is a lookup table that translates unicode characters drawn from the "Base64
   * Alphabet" (as specified in Table 1 of RFC 2045) into their 6-bit positive integer equivalents.
   * Characters that are not in the Base64 alphabet but fall within the bounds of the array are
   * translated to -1.
   */
  private static final byte base64ToInt[] = {-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
      -1, -1, -1,
      -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
      -1, -1, -1, 62,
      -1, -1, -1, 63, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, -1, -1, -1, -1, -1, -1, -1, 0, 1, 2,
      3, 4, 5, 6, 7,
      8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, -1, -1, -1, -1, -1, -1,
      26, 27, 28,
      29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51};
  /**
   * This array is the analogue of base64ToInt, but for the nonstandard variant that avoids the use
   * of uppercase alphabetic characters.
   */
  private static final byte altBase64ToInt[] = {-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
      -1, -1, -1, -1,
      -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, 0, 1, 2, 3, 4, 5, 6, 7, 8, -1,
      62, 9, 10,
      11, -1, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 12, 13, 14, -1, 15, 63, 16, -1, -1, -1, -1,
      -1, -1, -1, -1,
      -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, 17, -1, 18, 19, 21,
      20, 26, 27, 28,
      29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51,
      22, 23, 24, 25};

  /**
   * Translates the specified byte array into a Base64 string as per Preferences.put(byte[]).
   */
  public static String byteArrayToBase64(byte[] a) {
    return byteArrayToBase64(a, false);
  }

  /**
   * Translates the specified byte array into an "alternate representation" Base64 string. This
   * non-standard variant uses an alphabet that does not contain the uppercase alphabetic
   * characters, which makes it suitable for use in situations where case-folding occurs.
   */
  public static String byteArrayToAltBase64(byte[] a) {
    return byteArrayToBase64(a, true);
  }

  private static String byteArrayToBase64(byte[] a, boolean alternate) {
    int aLen = a.length;
    int numFullGroups = aLen / 3;
    int numBytesInPartialGroup = aLen - 3 * numFullGroups;
    int resultLen = 4 * ((aLen + 2) / 3);
    StringBuilder result = new StringBuilder(resultLen);
    char[] intToAlpha = (alternate ? intToAltBase64 : intToBase64);

    // Translate all full groups from byte array elements to Base64
    int inCursor = 0;
    for (int i = 0; i < numFullGroups; i++) {
      int byte0 = a[inCursor++] & 0xff;
      int byte1 = a[inCursor++] & 0xff;
      int byte2 = a[inCursor++] & 0xff;
      result.append(intToAlpha[byte0 >> 2]);
      result.append(intToAlpha[(byte0 << 4) & 0x3f | (byte1 >> 4)]);
      result.append(intToAlpha[(byte1 << 2) & 0x3f | (byte2 >> 6)]);
      result.append(intToAlpha[byte2 & 0x3f]);
    }

    // Translate partial group if present
    if (numBytesInPartialGroup != 0) {
      int byte0 = a[inCursor++] & 0xff;
      result.append(intToAlpha[byte0 >> 2]);
      if (numBytesInPartialGroup == 1) {
        result.append(intToAlpha[(byte0 << 4) & 0x3f]);
        result.append("==");
      } else {
        // assert numBytesInPartialGroup == 2;
        int byte1 = a[inCursor++] & 0xff;
        result.append(intToAlpha[(byte0 << 4) & 0x3f | (byte1 >> 4)]);
        result.append(intToAlpha[(byte1 << 2) & 0x3f]);
        result.append('=');
      }
    }
    // assert inCursor == a.length;
    // assert result.length() == resultLen;
    return result.toString();
  }

  /**
   * Translates the specified Base64 string (as per Preferences.get(byte[])) into a byte array.
   */
  public static byte[] base64ToByteArray(String s) {
    return base64ToByteArray(s, false);
  }

  /**
   * Translates the specified "alternate representation" Base64 string into a byte array.
   */
  public static byte[] altBase64ToByteArray(String s) {
    return base64ToByteArray(s, true);
  }

  private static byte[] base64ToByteArray(String s, boolean alternate) {
    byte[] alphaToInt = (alternate ? altBase64ToInt : base64ToInt);
    int sLen = s.length();
    int numGroups = sLen / 4;
    if (4 * numGroups != sLen) {
      throw new IllegalArgumentException("String length must be a multiple of four.");
    }
    int missingBytesInLastGroup = 0;
    int numFullGroups = numGroups;
    if (sLen != 0) {
      if (s.charAt(sLen - 1) == '=') {
        missingBytesInLastGroup++;
        numFullGroups--;
      }
      if (s.charAt(sLen - 2) == '=') {
        missingBytesInLastGroup++;
      }
    }
    byte[] result = new byte[3 * numGroups - missingBytesInLastGroup];

    // Translate all full groups from base64 to byte array elements
    int inCursor = 0, outCursor = 0;
    for (int i = 0; i < numFullGroups; i++) {
      int ch0 = base64toInt(s.charAt(inCursor++), alphaToInt);
      int ch1 = base64toInt(s.charAt(inCursor++), alphaToInt);
      int ch2 = base64toInt(s.charAt(inCursor++), alphaToInt);
      int ch3 = base64toInt(s.charAt(inCursor++), alphaToInt);
      result[outCursor++] = (byte) ((ch0 << 2) | (ch1 >> 4));
      result[outCursor++] = (byte) ((ch1 << 4) | (ch2 >> 2));
      result[outCursor++] = (byte) ((ch2 << 6) | ch3);
    }

    // Translate partial group, if present
    if (missingBytesInLastGroup != 0) {
      int ch0 = base64toInt(s.charAt(inCursor++), alphaToInt);
      int ch1 = base64toInt(s.charAt(inCursor++), alphaToInt);
      result[outCursor++] = (byte) ((ch0 << 2) | (ch1 >> 4));

      if (missingBytesInLastGroup == 1) {
        int ch2 = base64toInt(s.charAt(inCursor++), alphaToInt);
        result[outCursor++] = (byte) ((ch1 << 4) | (ch2 >> 2));
      }
    }
    // assert inCursor == s.length()-missingBytesInLastGroup;
    // assert outCursor == result.length;
    return result;
  }

  /**
   * Translates the specified character, which is assumed to be in the "Base 64 Alphabet" into its
   * equivalent 6-bit positive integer.
   *
   * @throw IllegalArgumentException or ArrayOutOfBoundsException if c is not in the Base64
   * Alphabet.
   */
  private static int base64toInt(char c, byte[] alphaToInt) {
    int result = alphaToInt[c];
    if (result < 0) {
      throw new IllegalArgumentException("Illegal character " + c);
    }
    return result;
  }

}